Temp. Gauge Issue

[Retnuh22]

1967 Dart
Replaced dash VL (brand:Standard)
I'm getting 12-13 volts to circuit board and pulsating volts (0-6 or so) to gauges.

As the vehicle sits cold, the gauge needle sits below the Cold mark. Warm the vehicle up to at least 180 degrees from cold and the needle moves to the Cold line and moves no further. Vehicle is turned off, and the key is then turned to Run. The needle rises to approximately half way, then slowly lowers to the cold line. The vehicle is then started and again the needle moves half way then slowly moves to the Cold line.

Grounding gauge wire makes the needle move to hot, so it appears to be okay.

My question is, what would cause the needle to rise where it should be, but then fall to the cold mark knowing the car it to temp (confirmed with infrared)

And... just so you all know, I'm also having issues with the fuel gauge as it doesn't read correct (normal from what I have read). New tank and sender, grounded as designed. The needle goes from empty on startup, and has choppy movement up to the quarter tank mark (the movement is not smooth).

Any input would be helpful.

Garret

 

[67Dart273]

The first thing to do is get some resistors and see if the gauges "have a chance" of reading correct. This includes problems with the gauge units, wiring / connection problems, including the PC board, and the IVR unit itself.

The resistances are

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

you don't need exact. Electronics suppliers such as Mouser, Digikey have these. You used to be able to get them at RadShack. I've got some if you cannot find them let me know.

You just put a resistor from the wire to ground, turn the key on for a couple of minutes to let it stabilized, and the gauge should read close to the resistance indicated, IE 23-25 ohms should give you close to 1/2 scale on the gauge.

 

[gdizzle]

in my limited experience a choppy needle move is a sign of a burned out, damaged gauge. How is the gas gauge?

 

[Retnuh22]

I'm sorry if I wasn't clear:

Temp gauge moves in a smooth motion from below cold to the cold mark. And when key is turned off and back on the needle moves from below cold to midway in a smooth motion then drops to cold for no reason (of course there is a reason but that is the issue)

The fuel gauges is choppy to a quarter full (ohms read 34 or so) and if it suppose to drop when the key is turned off, it does not.

The resistors are a good idea for sure. I thought by grounding the harness and getting full smooth motion, that the gauges would be good to use (though may be inaccurate). I have also found the circuit boards have had some soldering done to them. Would that maybe give the gauges bad voltage? There are wires soldered from the harness pins to the printed circuit..
I might have better luck wth new/used boards?

Garret

 

[67Dart273]

If the gauge does not drop with power shut off, the guage itself is screwed up.

 

[Retnuh22]

Well, that helps with the fuel gauge issue ;). Thank you.

 

[Retnuh22]

And...maybe not, just went out to the garage and the needle has moved down to empty... Argh...

 

[RedFish]

Wild needle swings are result/evidence of failing instrument voltage regulator. I've seen temp gauge needles race to full hot before slowly dropping back to proper reading.
Absolutely no doubt this is the problem. You're welcome

 

[Retnuh22]

I have replaced the dash voltage limiter twice now with the same result. (Same part number and brand: Standard- VRC-601). Is this the correct part? And if so,does anyone know of another brand or type of limiter to try?

** just to be sure, the capacitor pin goes into the same female slot as the 12v connection?

Garret

 

[67Dart273]

Yes the cap goes to the 12V connection. The problem you have is not the VR if the gauge is acting up AFTER you shut off the key

 

[jimjimjimmy]

I have replaced the dash voltage limiter twice now with the same result. (Same part number and brand: Standard- VRC-601). Is this the correct part? And if so,does anyone know of another brand or type of limiter to try?

** just to be sure, the capacitor pin goes into the same female slot as the 12v connection?

Garret

http://rt-eng.com/rte/index.php/RTE_limiter this one works great

 

[Retnuh22]

So, I found the following resistors at Radio Shack;

10.0 / 22.0 / 68.0 (they are as close as I could find to 67dart273 recommendations)

I have placed them in-line with a ground to temp gauge harness and observersd the following:

10.0 resulted in the needle moving to just over half way
22.0 resulted in the needle moving to just over the cold mark
68.0 resulted in the needle staying well below the cold mark

When the car is to tempurature, with a 180 thermostat and harness connected to the temp sensor, the needle runs just over the cold mark. Is there any way to some how adjust the gauge to be zeroed out at the cold mark at the 10 ohms? I have replaced the temp sensor with a Standard- TS17T. I will verify it has the correct ohm range needed. I have taken pictures of each result. Please let me know if you would like to see the results to compare.

Garret

 

[RedFish]

It is possible that a bad limiter damaged the temp gauge. Good luck with it.

 

[67Dart273]

So, I found the following resistors at Radio Shack;

10.0 / 22.0 / 68.0 (they are as close as I could find to 67dart273 recommendations)

I have placed them in-line with a ground to temp gauge harness and observersd the following:

10.0 resulted in the needle moving to just over half way
22.0 resulted in the needle moving to just over the cold mark
68.0 resulted in the needle staying well below the cold mark

When the car is to tempurature, with a 180 thermostat and harness connected to the temp sensor, the needle runs just over the cold mark. Is there any way to some how adjust the gauge to be zeroed out at the cold mark at the 10 ohms? I have replaced the temp sensor with a Standard- TS17T. I will verify it has the correct ohm range needed. I have taken pictures of each result. Please let me know if you would like to see the results to compare.

Garret

Now run the same check on the fuel gauge. If they both read the same, you at least have an IVR problem. If the fuel gauge reads "more correct" then the gauge unit is probably toast. Don't forget to "tighten / loosen tighten" the stud nuts on the gauge, "HOWEVER": your previous description of the gauge sticking there with key off does not sound good for the gauge unit.